The Citadel

The Citadel​ is a sprawling megacity and the ancestral homeland of all Tritons. It lies 4000 meters beneath an archipelago of small volcanic islands off the Eastern coast of Varonia.

The Archipelago
Merfolk are native to the shallow waters of the islands. Their self-governing tribes prefer a provincial lifestyle of fishing and cultivating ocean crops. Coral reefs act as protection from their natural predators: large, shark-like humanoids called the Sahuagin who surface from twilight waters to hunt. (200-1000 meters)

Deeper Waters
Past the twilight and into the midnight zone, light from the surface disappears altogether and pressure becomes deadly to those unaccustomed or unprepared. Where bases of the islands slope off into the abyssal plain, the active geology of the area becomes apparent. Hydrothermal vents clustered about the seafloor send up jets of magma-heated seawater, along with minerals from below the earth's crust. These vents have formed an oasis where a strange and alien ecosystem flourishes.

City Structure
There are no proper territories at the bottom of the ocean. Small settlements are unheard of, as they are impractical to defend and every Triton is well aware that safety is in numbers.

Though mostly submerged, a great portion of the city breaches into the open air of a massive underwater cavern miles below the surface of the sea. Tritons have developed sophisticated forms of magic to power their cities and ways of everyday life. Powerful wards and protective barriers also provide the majority of the city’s protection.

The Citadel is built in vertical tiers, with about 1/3 of its massive structure rising above water level.

Tiers

 * Topside: portion above water in the cavern. Mostly public works and upperclass residences
 * The Spire: extends out of water in the center. Home to the councilhead
 * Netherside: below water level. A dense, urban area.
 * The Underbelly: a system of lava tubes extending from the base of the cavern. Claustrophobic, poorly lit, and uncomfortably warm because of its proximity to the vent. Elemental generators are located here

The Trench
Bright lights from the city tend to attract creatures from even darker waters. Not far from the Citadel, a deep trench cuts through the plain: a portal to an unknown underworld that all Tritons fear. Sea-serpents and other monstrosities emerge from time to time to feed on the flourishing marine life that has made its home around the vents.

In the last century, a great elemental barrier has been completed which encloses the large cavern opening and protects the Citadel from these large predators. It is maintained by magical generators which harness the earth's volcanic activity in the form of concentrated abjuration magic.

Tritons don't venture out across the seafloor. Leaving and entering is done through lava tubes that open up closer to the surface. Tunnels that open out onto open ocean have large grates installed that allow medium-sized creatures through, but keep larger predators like the Sahuagin out. The Citadel posts border guards at these points of entry.